OK, I now also have the same problem. I'm trying to determine if the 3/4 NTP is the same thread size/pitch as the 3/4" galvanized plug at Lowes (or the 3/4" gas black pipe). The threads line up with my old plug. I just want to make sure before trying to get these one.

I couldn't find a brass fitting (tee, reducer) to match the same thread pitch. The ones I found were more coarse.....like a hose type thread. I saw a lot of MIP type threads, but no NTP's.